By NICHOLAS BAKALAR

Published: July 10, 2012

Methadone accounted for almost a third of the deaths caused by opioid pain relievers in 2009, even though it was prescribed far less often than other such drugs, government researchers have found.

Researchers writing in last week's Morbidity and Mortality Weekly Report crunched data from the National Vital Statistics System and the Drug Enforcement Administration. The rate of overdose deaths involving methadone in 2009 was more than five times the rate in 1999, they found. The drug accounted for 1.7 percent of the 257 million prescriptions written in 2009 for opioid pain relievers, but it was involved in 31.4 percent of overdose deaths and more than 40 percent of the deaths attributable to use of a single drug.

Methadone has a longer duration of action than other opioids, and it is inexpensive, which may help explain its increasing use since 1999. But it can accumulate in the body to toxic levels, leading to respiratory depression and heart rhythm problems.

''We're not talking about methadone maintenance treatment programs in this data,'' said Dr. Thomas R. Frieden, the director of the Centers for Disease Control and Prevention. ''All of the evidence suggests that the increase in methadone deaths is related to the increased use of methadone to treat pain. There are plenty of safer alternatives.''

This is a more complete version of the story than the one that appeared in print.